Why Are Flame Retardant and Fire Resistant Cables Crucial for Fire Safety in South Africa?

The Importance of Cable Selection in Fire Safety

Fire safety in buildings and industrial settings hinges on meticulous planning, and cable selection plays a starring role. Whether in Johannesburg’s towering skyscrapers, Cape Town’s busy airports, or the deep mines of Mpumalanga, the right cables can mean the difference between a safe evacuation and a catastrophe. Flame retardant and fire resistant cables are designed to enhance safety, but they serve distinct purposes. Understanding these differences ensures compliance with South African standards, such as SANS 10142 for electrical installations, and protects lives in high-risk environments like public spaces and industrial facilities.

This article aims to clarify the properties, applications, and standards of these cables, with a focus on their relevance to South Africa’s unique landscape. From underground transport systems to hospitals, choosing the right cable is a matter of safety, compliance, and practicality.

What Are Flame Retardant and Fire Resistant Cables?

Flame Retardant Cables

Flame retardant cables are engineered to limit the spread of fire. Their defining trait is their ability to self-extinguish once the flame source is removed, preventing fire from racing along the cable. However, these cables are not designed to maintain circuit integrity during a fire, meaning they may fail to function under prolonged fire exposure.

These cables often incorporate Low Smoke Zero Halogen (LSZH) materials, which produce minimal smoke and non-toxic gases when burned. This makes them ideal for enclosed spaces where smoke inhalation and poor visibility could hinder evacuation. Flame retardant cables are tested to international standards like IEC 60332-1-2 for single cables and IEC 60332-3 for bunched cables to ensure they resist flame propagation. Additionally, LSZH variants undergo IEC 60754 (acid gas emission) and IEC 61034 (smoke emission) tests to confirm low toxicity and smoke density.

Fire Resistant Cables

Fire resistant cables, on the other hand, are built to maintain circuit integrity—the ability to continue functioning during a fire for a specified period. These cables ensure that critical systems, such as fire alarms, emergency lighting, and sprinkler pumps, remain operational, aiding evacuation and firefighting efforts.

A key feature of fire resistant cables is the inclusion of a fire-resistant layer, typically mica tape, wrapped around copper conductors. Mica, a natural mineral with high dielectric strength and heat resistance, acts as a fire barrier, preserving circuit functionality even at extreme temperatures. Fire resistant cables are rigorously tested to standards like BS 6387 (Category CWZ), IEC 60331, SS 299, BS EN 50200, and BS 8434-2, which assess resistance to fire, fire with water, and fire with mechanical shock. Standard fire resistant cables maintain integrity for at least 30 minutes, while enhanced versions endure for 120 minutes or more.

Key Terminology

• Flame propagation: The spread of fire along a cable’s surface, which flame retardant cables are designed to minimise.

• Circuit integrity: The ability of a cable to maintain electrical functionality during a fire, a hallmark of fire resistant cables.

• LSZH: Low Smoke Zero Halogen materials that emit minimal smoke and non-toxic gases, enhancing safety in fire scenarios.

Structural and Material Differences

Flame Retardant Cables

Flame retardant cables share a similar structure to standard cables but incorporate flame-retardant materials in their insulation, sheathing, or auxiliary components (e.g., banding or filling). Common materials include LSZH compounds and fluoropolymers like ETFE, FEP, and PTFE, which are highly effective at resisting flame spread. These cables are tested to IEC 60332-1-2 (single cable flame propagation) and IEC 60332-3 (bunched cables under fire conditions). For LSZH variants, additional tests like IEC 60754 and IEC 61034 ensure minimal acid gas and smoke emissions, critical for safety in enclosed spaces.

Fire Resistant Cables

Fire resistant cables are structurally distinct, featuring a mica tape layer between the copper conductor and insulation. Copper, with its high melting point of 1083°C, ensures the conductor remains functional under intense heat. The mica tape provides a robust fire barrier, enabling the cable to maintain circuit integrity. These cables undergo stringent testing to standards like BS 6387 (Cat. CWZ), which evaluates performance under fire, water, and mechanical shock, and IEC 60331 for fire resistance. Standard cables are tested to BS EN 50200 for 30-minute circuit integrity, while enhanced cables meet BS 8434-2 for 120-minute endurance.

Material Comparison

Flame retardant cables prioritise self-extinguishing properties and low smoke emission, using materials like LSZH and fluoropolymers to limit fire spread and toxicity. Fire resistant cables focus on heat resistance and operational continuity, leveraging mica tape and copper conductors to withstand fire conditions. Both cable types may use LSZH materials, but their structural and functional goals differ significantly.

Applications in Fire Safety

Flame Retardant Cables

Flame retardant cables are ideal for non-emergency circuits, such as those powering general lighting, sockets, and appliances like printers, kettles, or TVs. Their ability to limit flame propagation and reduce smoke and toxic gas emissions makes them perfect for enclosed, high-traffic areas like airports, schools, hospitals, shopping centres, and underground transport systems. In South Africa, where urban density and public spaces are common, these cables enhance evacuation safety by minimising smoke-related risks.

Fire Resistant Cables

Fire resistant cables are indispensable for emergency systems that must remain operational during a fire. These include fire alarms, voice alarm systems, emergency lighting, and sprinkler pumps. They are critical in large or complex buildings, such as high-rise office blocks in Sandton or industrial facilities in Rustenburg, where prolonged circuit integrity is vital for safe evacuation and firefighting. These cables ensure that life-saving systems function for at least 30 minutes (standard) or up to 120 minutes (enhanced), depending on the application.

South African Context

In South Africa, compliance with SANS 10142, the national standard for electrical installations, is paramount. Flame retardant and fire resistant cables are widely used in high-risk environments like mines, where fire hazards are amplified by confined spaces, or in public spaces like shopping centres and transport hubs. The country’s growing urbanisation and industrial activity underscore the need for cables that meet both local and international safety standards, ensuring reliability in diverse applications.

Testing and Standards

Flame Retardant Cables

Flame retardant cables are tested to IEC 60332-1-2 for single cables and IEC 60332-3 for bunched cables to verify their ability to limit flame propagation. LSZH variants undergo IEC 60754 to measure acid gas emissions and IEC 61034 to assess smoke density, ensuring they meet safety requirements for enclosed spaces.

Fire Resistant Cables

Fire resistant cables face more rigorous testing to confirm circuit integrity under fire conditions. Standards like BS 6387 (Cat. CWZ) evaluate resistance to fire, fire with water, and fire with mechanical shock. IEC 60331 tests fire resistance, while BS EN 50200 ensures 30-minute circuit integrity for standard cables. Enhanced cables are tested to BS 8434-2 for 120-minute performance under harsher conditions, including direct flame, impact, and water jets.

Importance of Compliance

Adhering to these standards ensures that cables perform reliably in fire scenarios, protecting lives and property. In South Africa, compliance with SANS 10142 aligns installations with local safety regulations, making it critical for engineers and contractors to select certified cables for public and industrial applications.

Low Smoke Zero Halogen (LSZH) Explained

What is LSZH?

Low Smoke Zero Halogen (LSZH) materials are a cornerstone of modern fire safety cables. Unlike PVC (polyvinyl chloride), which releases black smoke and toxic hydrogen chloride (HCl) gas when burned, LSZH materials produce minimal smoke and non-toxic residues. PVC combustion results in hydrochloric acid formation when HCl reacts with moisture in the eyes, mouth, or throat, causing irritation and hindering evacuation. LSZH materials, containing inorganic additives like aluminium hydroxide or magnesium hydroxide, release water vapour when burned, reducing fire intensity and toxicity.

Chemical Reactions

• PVC: (CH2CHCl)n + O2 → CO2 + CO + HCl + H2O (produces toxic HCl gas, posing health risks).

• LSZH: Mg(OH)2 → MgO + H2O or 2Al(OH)3 → Al2O3 + 3H2O (releases water vapour, reducing fire intensity and producing non-toxic residues).

Benefits of LSZH

LSZH materials enhance visibility and reduce health risks during evacuation by minimising smoke and acidic gas emissions. Their use in both flame retardant and fire resistant cables makes them a preferred choice in South Africa’s safety-conscious environments, from hospitals to public transport systems.

Choosing the Right Cable

Factors to Consider

Selecting the right cable depends on several factors:

• Application: Emergency systems (e.g., fire alarms) require fire resistant cables, while non-emergency circuits (e.g., general lighting) can use flame retardant cables.

• Environment: Enclosed spaces or high-risk areas like mines demand LSZH cables to reduce smoke and toxicity.

• Regulatory requirements: Compliance with SANS 10142 and international standards ensures safety and legality.

Decision Guide

• Flame retardant cables: Use for general power distribution to non-critical systems, such as office lighting or appliances, in enclosed spaces.

• Fire resistant cables: Use for life safety and firefighting systems, such as fire alarms and emergency lighting, where circuit integrity is critical.

Cost and Practical Considerations

Fire resistant cables are more expensive due to specialised materials like mica tape and rigorous testing requirements. Flame retardant cables are more cost-effective for non-critical applications, making them a practical choice for general use. Balancing cost and safety is key, particularly in budget-conscious South African projects.

FAQs

What is the main difference between flame retardant and fire resistant cables?

Flame retardant cables prevent fire spread but do not maintain functionality during a fire. Fire resistant cables maintain circuit integrity for emergency systems, ensuring operation for 30–120 minutes.

When should I use flame retardant cables?

Use them in non-emergency circuits, like general lighting or appliances, in enclosed spaces to reduce fire spread and smoke.

When should I use fire resistant cables?

Use them in emergency systems, such as fire alarms and emergency lighting, to ensure functionality during a fire.

What does LSZH mean, and why is it important?

LSZH (Low Smoke Zero Halogen) materials reduce smoke and toxic gas emissions, improving visibility and safety during evacuation.

Are flame retardant cables suitable for emergency systems?

No, they are not designed to maintain circuit integrity during a fire and should not be used for emergency systems.

What standards apply to these cables in South Africa?

Flame retardant cables: IEC 60332, IEC 60754, IEC 61034. Fire resistant cables: BS 6387, IEC 60331, BS EN 50200, BS 8434-2, aligned with SANS 10142.

How do LSZH materials work in a fire?

LSZH materials release water vapour when burned, reducing fire intensity and producing non-toxic residues, unlike PVC, which releases harmful HCl gas.

Conclusion

Flame retardant and fire resistant cables are vital for fire safety, each serving distinct roles. Flame retardant cables limit fire spread and smoke, making them ideal for non-critical systems in enclosed spaces. Fire resistant cables ensure circuit integrity for emergency systems, supporting evacuation and firefighting in high-risk scenarios. In South Africa, where urban and industrial environments demand robust safety measures, selecting the right cable is critical. Compliance with SANS 10142 and international standards, coupled with the use of LSZH materials, enhances safety and reliability. Consult certified electrical engineers and adhere to local regulations to choose cables that protect lives and property effectively.